1. Field of the Invention
The present invention relates to a liquid handling method and an apparatus therefor for use in an imaging apparatus utilizing liquid development and image transfer, and capable of preventing the intrusion of unnecessary liquid into the area within the developed image before transfer is formed.
2. Description of the Prior Art
For the purpose of obtaining a visible image from an electrostatic image formed on an image carrier by means for example of an electrophotographic process, the liquid development process has been in wide use because of the tonal rendition thereof.
The surface of such image carrier developed with such liquid development process inevitably carries a certain amount of excessive liquid developer which has to be eliminated regardless whether the developed image is to be fixed on said image carrier or is to be transferred onto a transfer material.
Particularly in the field of the transfer processes in which the image obtained by liquid development is transferred onto a transfer material, there have been proposed various methods to eliminate such excessive developer in order to obtain a satisfactory transferred image.
In such liquid development process involving the image transfer, the elimination of excessive liquid developer is particularly important as an elevated amount of the excessive liquid developer, if present on the transfer material, will render the rapid fixation of the transferred image on the transfer material difficult. Also in such case, the fixation, which is usually achieved by heating, will consume an elevated amount of thermal energy for evaporating said excessive liquid developer, thus wasting the energy, resulting in a higher load to the fixing means and thereby leading to a larger space therefor.
Besides the transfer material containing an elevated amount of excessive liquid developer may not be completely dried even after passing the fixing means and be delivered to the user in a wet state, thus staining the hands of the user or other articles which may come into contact therewith.
Furthermore, the image transfer, if conducted in the presence of an elevated amount of the excessive liquid developer, will easily result in image streaking and thus is unable to maintain a satisfactory image quality. In order to prevent the foregoing drawbacks the excessive liquid developer is squeezed off from the surface of the image carrier, and such squeezing can be achieved for example by an air-knife method utilizing an air flow directed toward the surface of said image carrier as disclosed in the U.S. Pat. No. 3,741,649, by a corona squeezing method utilizing a corona discharge from a corona discharger as disclosed in the U.S. Pat. No. 3,722,994, or by a roller squeezing method utilizing a roller rotated at a determined distance from the surface of said image carrier as disclosed in the U.S. Pat. No. 3,957,016, among which the latter two are widely used in practice.
These known methods, however, are defective in that the squeezing may often not be achieved effectively and become uneven in the lateral edge portions of the surface of the image carrier. Various improvements proposed to overcome this defect has not necessarily been successful. In addition to the foregoing, the present inventors have found that a satisfactory transferred image cannot be obtained by simply squeezing off the excessive liquid developer present on the surface of the image carrier.
In fact the present inventors have found a fact that the thickness of liquid layer on the surface of the image carrier holding thereon the developed image before the image transfer is perturbed by a stray flow of the liquid developer removed in the cleaning section or overflowing from the developing section to the lateral portions of the image carrier.
The use of a cleaning liquid is currently done in commercially available apparatus for achieving an effective cleaning, and a considerable amount of the stray flow as explained above is particularly inevitable in such apparatus. Although the decrease in the amount of the cleaning liquid allows to reduce the amount of such stray flow in such case, it will result at the same time in a reduced cleaning efficiency, thus undesirably affecting the recycling of the image carrier and the image quality.
The present invention has been achieved in consideration of the foregoing drawbacks.